Between ten and twenty percent of people worldwide develop atopic dermatitis — a term that is sometimes used interchangeably with eczema to describe skin conditions characterized by irritated, inflamed, itchy patches. People who have atopic dermatitis have long-lasting dermatitis symptoms, and they often have a history of allergies, asthma, and one or more family members who have experienced atopic dermatitis. In some people, atopic dermatitis causes the skin to appear very red with a rash that seems to bubble up; in others it can appear scaly, flaky, and dry with less discoloration. Atopic dermatitis is not contagious and is believed to result from genetic factors that influence the function of the skin, causing it to be extra sensitive to irritants.
Your skin is composed of two main regions: the epidermis and the dermis. The epidermis is the outer layer that acts as the body’s primary defense against the environment. It keeps out germs and allergens, which are substances to which the body produces an allergic response. The dermis lies beneath the epidermis and is responsible for providing structure and support to the skin. On most of the body, the epidermis is actually comprised of four distinct layers as shown. Cells produced in the stratum basale are pushed outward as new cells develop, and they gradually die as they migrate to the stratum corneum at the surface where they eventually slough off. Normally, the rate of skin production and loss are equal so that the thickness of this outer layer remains constant. However, in some instances more skin cells may be shed from the stratum corneum than accumulate or excessive skin cells may accumulate as abnormally thickened skin.
Atopic dermatitis is believed to result from how a person’s genes influence their immune response and formation of the epidermis. Researchers don’t know the exact cause, but there are two primary theories. In one, it is believed that genetic factors influence the immune system in the skin, causing it to react as if a person has contacted something to which they are allergic. A series of internal reactions cause itchiness and inflammation that damages the skin’s barrier layer (stratum corneum). The damage results in increased water loss through the epidermis, resulting in dry patches and further degradation. Allergens and germs may enter the eroded skin, setting off more reactions. In another theory, it is believed that a person’s genes cause the outer layer (stratum corneum) of skin to be abnormal and ineffective as a barrier. Excessive water is lost through the skin, causing dryness and a breakdown of the outer layer. Allergens and germs are able to penetrate, starting a cycle of itchiness and inflammation that further erodes the skin.
The majority of patients with atopic dermatitis have regions that are constantly itchy, even when there are no other symptoms. When inflammation develops from atopic dermatitis, it irritates patches of skin, causing them to redden and become so itchy that it is hard to resist scratching. Regions of elevated, fluid-filled bumps may potentially develop. With continued irritation, these bumps may burst and exude pus and become crusty, or the skin may become dry and cracked. Although atopic dermatitis is not commonly associated with life-threatening risks, if scratching the itch causes openings through the skin that penetrate into the dermis, germs may enter and cause a secondary infection. In some people, the skin responds to continued, long-term scratching of itchy areas by producing an excessively thick outer layer. This process, which is called lichenification, results in the skin having a leathery, cracked appearance.
The majority of cases of atopic dermatitis begin during the first year of life, and about ninety percent of cases first occur before age five. Although it is rare, atopic dermatitis can also first occur at the onset of puberty or later during adulthood. Active atopic dermatitis can disappear entirely, or it may enter a period of remission and recur as a flare-up at some point in the future. About half of the atopic dermatitis cases in infants clear by a year and a half to two years of age, while others take longer or may never completely disappear. A person may continue to exhibit signs into adulthood, primarily on the hands, and symptoms elsewhere can recur periodically at any age.
In infants, atopic dermatitis typically appears on the scalp, forehead, cheeks, neck, forearms, and legs. In contrast, children and adults most commonly experience patches of atopic dermatitis on the face, neck, upper chest, elbow creases, wrists, hands, fingers, back of the knees, ankles, and feet. Although there are tendencies, atopic dermatitis can occur on any part of the body at any age, and it may be triggered by a variety of irritants that vary from person to person. These irritants include dry skin, sudden temperature changes, abrasive fabrics, certain chemicals and smoke, various food items, substances from living organisms, and environmental factors as shown. Sometimes triggers can be identified with skin allergy tests, but often they are difficult to determine and are only identified after observing changes in one’s diet or the products one uses and noting when and how symptoms worsen or improve over time.
There is no cure for atopic dermatitis, but it can often be managed with treatment, avoiding triggers, and taking preventative actions. Keeping fingernails short and resisting the urge to scratch can also prevent making conditions worse. Sleeping in hand mitts may help children, who find it particularly difficult to resist scratching. Bathing in lukewarm water, using special soaps, and applying moisturizers directly after bathing are also often effective in clearing symptoms. New products designed to limit water loss and improve the structure of the skin barrier are also effective in many patients. Although not always necessary, the primary medications used for treating atopic dermatitis include moisturizers, which reduce dryness; corticosteroids, which reduce swelling and reduce itchiness; immune modulators, which suppress the skin’s immune response; and antihistamines, which reduce itchiness.
Fortunately, a childhood onset of atopic dermatitis will usually resolve naturally over time. In people with persistent or recurring symptoms, available treatment options can help control atopic dermatitis. Consulting a health care provider can help you more rapidly identify triggers, manage the symptoms of flare-ups, and find the best treatment option for your particular skin. Although there is no cure, symptoms can usually be managed well enough to lead a comfortable, productive life.
Affected areas may also be reddened, inflamed, and cause an itching or burning sensation. A mild form of seborrheic dermatitis on the scalp is one cause of dandruff. Seborrheic dermatitis is not contagious, meaning it cannot be acquired through contact with a person who has this skin condition. This animation will describe the possible causes of seborrheic dermatitis, how and where this skin condition occurs, and options that are available to treat it.
To understand how seborrheic dermatitis occurs, it is important to understand some of the basic anatomy of your skin. Your skin is composed of two layers, known as the epidermis and the dermis. The epidermis serves as your skin’s primary defense against the environment. The dermis provides your skin with structure, support, and elasticity. Sebaceous glands are found within the dermis, typically near hair follicles, although they can occur in hairless areas as well. These glands secrete an oily substance known as sebum, which lubricates the surface of your skin and prevents it from drying out.
The exact cause of seborrheic dermatitis is unknown. One theory proposes that seborrheic dermatitis is a reaction to particular types of yeast (Malassezia genus), which are single-celled organisms that are commonly found on human skin. Typically, the yeast cause no problems, but in some people when the yeast metabolize sebum, they generate byproducts that irritate the skin. Another theory, which complements the yeast theory, suggests that seborrheic dermatitis may result from excessive sebum production. Yeast are found in sebum rich areas and may be more likely to cause skin irritation in areas of the skin that produce excessive sebum. An additional factor believed to be linked to seborrheic dermatitis is an increased level of the hormones known as androgens, which control sebaceous gland activity. Seborrheic dermatitis is more frequent in males, who produce more androgens than females, temporarily in infants who have been exposed to high androgen levels in the womb, and following puberty, when androgen levels increase in both sexes.
Seborrheic dermatitis usually occurs after puberty, affecting people between the ages of 20 and 50, although it can also occur in infants. In infants this condition has been termed “cradle cap”, since it typically affects the scalp, and it usually disappears spontaneously by six months to one year of age. Seborrheic dermatitis arises most frequently in males and in persons affected by a central nervous system disorder, such as major paralysis or Parkinson’s disease. Seborrheic dermatitis primarily affects areas of the skin that have the most numerous and active sebaceous glands. These areas include the scalp, hairline, eyebrows, eyelashes, creases of the nose, external ear canal, skin behind the ears, and areas along skin folds of the trunk, such as the armpits, navel, groin, and buttocks. In infants, in addition to “cradle cap” on the scalp, seborrheic dermatitis can also affect the face and diaper area.
In most cases of mild seborrheic dermatitis, cleansing daily with an anti-dandruff shampoo is recommended. Washing the affected areas with a mild soap or soapless cleanser may also help decrease surface sebum. If symptoms persist despite daily cleansing, additional treatment options are available, including anti-fungal medications used to control the growth of yeast and anti-inflammatory medications used to reduce redness and inflammation. Lotions and creams containing ingredients such as coal tar, corticosteroids, salicylic acid, selenium, sulfur products, and zinc may be advised to clear more persistent scales. In addition, some people notice that sunlight exposure improves their symptoms.
Although there is no cure, the symptoms of seborrheic dermatitis can usually be managed successfully, allowing people to lead comfortable, productive lives. Several treatment options are available, and finding the right treatment to fit your specific needs may take time. It is suggested that you begin with mild treatments and switch to more intensive treatments if necessary. Consulting a health care provider can help you identify the best treatment option for your particular skin and seborrheic dermatitis symptoms.